1. Field of Invention
The present invention relates to a drainage structure of an electric parts accommodation box disposed in an engine compartment. More particularly, the present invention is intended to efficiently drain any liquid that has penetrated into a box accommodating a battery fuse mounted on a battery.
2. Description of Related Art
In the electric parts accommodation box disposed in an engine compartment or the like into which water penetrates, water which has penetrated into the electric parts accommodation box is drained from an opening formed in a drainage port provided on a bottom wall thereof, as disclosed in Japanese Utility Model Application Laid-Open Nos. 7-27235 and 7-3233 and Japanese Patent Application Laid-Open No. 9-102264.
As shown in FIG. 8A, a bottom wall 1 inclines downward toward a drainage port 1a to collect water inside the electric parts accommodation box to the drainage port 1a and discharge it to the outside.
When the drainage port 1a is formed at the lowermost portion of the inclined bottom wall 1, water can be drained from the drainage port 1a when a large amount of water has penetrated into the fuse box. On the other hand, when a small amount of water penetrates into the fuse box, as shown in FIG. 8B, droplets may stick to the periphery of the drainage port 1a of the bottom wall 1. In other words, water 100 may remain on the bottom wall 1. Therefore, the water 100 cannot be efficiently drained from the drainage port 1a. 
As shown in FIG. 9, a battery terminal 3 connected to an end of a lead wire 4 is fitted on the periphery of a battery post 2 projecting from the upper surface of a battery 1. The lead wire 4 is wired to a fuse box 5 to connect the lead wire 4 to a fuse accommodated inside the fuse box 5.
Because this kind of the fuse box is disposed in the engine compartment proximate to the battery, water penetrates into the fuse box. Thus, it is necessary to efficiently drain the water that has penetrated into the fuse box to the outside.
In the fuse box 5 shown in FIG. 9A, it is necessary to connect the battery fuse and the battery 1 with each other through the lead wire 4. Thus, much time and labor are required, and a large number of component parts are required. In addition, a large installing space is required for the fuse box 5. There is a demand for a construction in which the fuse box 5 is directly mounted on the battery 1 to connect the battery fuse and the battery 1 to each other without using the lead wire 4. In this case, the fuse box accommodates the battery fuse, a bus bar connected to the terminal of the battery fuse, and a battery terminal connected to the bus bar to be connectedly fitted on the periphery of the battery post of the battery.
Because the fuse box is mounted on the upper surface of the battery, it is desirable to reduce the height of the fuse box as much as possible. Therefore, as shown in FIG. 9B, a gap S is very short between the bus bar 7 accommodated in the box 6 and the bottom wall 6a of the box 6. However, water sticks to the periphery of the drainage port 6b of the bottom wall 6a. Consequently, even a small amount of water collected in the gap S may cause a current leak or electrical short to occur between adjacent bus bars 7A and 7B through the water.
The present invention has been made in view of the above-described problem. Accordingly, it is an object of the present invention to provide an electric parts accommodation box having a structure capable of draining even a small amount of water from a drainage port to prevent a current leak or electrical short from occurring between electric parts, such as bus bars, when the length of the gap between a bottom wall of the electric parts accommodation box and the electric parts is short.
To achieve the object, according to the present invention, there is provided a drainage structure of an electric parts accommodation box including a drainage port formed on a bottom wall thereof; a cut-out portion, continuous with the drainage port, a tip of which tapers off to form an acute angle; and a water-leading groove, continuous with the tip, formed on an outer surface of the bottom wall. With this, a droplet that sticks to the water-leading groove disposed on the outer surface of the bottom wall is brought into contact with a droplet that sticks to the tip of the cut-out portion disposed on an inner surface of the bottom wall to flow out a droplet that sticks to a peripheral edge of the drainage port to the outer surface of the bottom wall.
A thin inclined portion may be formed on the outer surface of the bottom wall toward the peripheral edge of the drainage port. The water-leading groove is formed on the inclined portion. The water-leading groove allows droplets drawn out to the outside from the tip of the cut-out portion to be drained easily from the electric parts accommodation box.
Preferably, the drainage port has an approximately square central hole approximately square and a triangular cut-out portion formed at a center of at least one side of the central hole. The triangular cut-out portion is continuous with the central hole. The tip of the triangular cut-out portion is continuous with a tip of the water-leading groove.
Since the central hole is continuous with the triangular cut-out portion, droplets sticking to the peripheral edge of the drainage port can be collected easily to the tip of the cut-out portion. Since the tip of the triangular cut-out portion is continuous with the tip of the water-leading groove, it is possible to smoothly drain droplets sticking to the inner surface of the bottom wall.
The drainage structure of the electric parts accommodation box includes a fuse box, mounted on an upper surface of the battery box, that accommodates a battery fuse and bus bars connected to terminals of the battery fuse. With this, a battery terminal to be fixed to a periphery of a battery post projecting from the upper surface of the battery box is connected to the bus bars. Also, the drainage port and the water-leading groove are formed on a lower case of the fuse box so that water that has penetrated into the fuse box is drained from the drainage port.
The drainage port and the water-leading groove are formed on a lower case of the fuse box so that water that has penetrated into the fuse box is drained from the drainage port.
According to experiments conducted by the inventors, it has been demonstrated that when a droplet that sticks to the tip of the cut-out portion continuous with the drainage port disposed on the inner surface of the bottom wall of the electric parts accommodation box contacts and coalesces a droplet that sticks to a tip of the water-leading groove disposed on the outer surface of the bottom wall thereof, the droplet on the inner surface of the bottom wall is drawn out to the outer surface of the bottom wall.
The fuse box, accommodating the battery fuse, has the above-described construction to reliably draining water which has collected on the inner surface of the bottom wall of the lower case thereof to the outside. Thus, it is possible to prevent a current leak from occurring between bus bars, even though the lower case and the bus bars are disposed proximately.